In maize, stalk lodging, or stalk breakage, accounts for significant annual yield losses in the United States. During a maize plant's vegetative growth phase, rapid growth weakens cell walls, making stalk tissue brittle and increasing the propensity for stalks to snap when exposed to strong, sudden winds and/or other weather conditions. This type of stalk lodging, called green snap or brittle snap, typically occurs at the V5 to V8 stage, when the growing point of a maize plant is emerging from the soil line, or at the V12 to R1 stage, about two weeks prior to tasseling and until just after silking. Another type of stalk lodging, late season stalk lodging occurs near harvest when the stalk cannot support the weight of the ear. Factors that weaken the stalk during late season include insect attack, such as the European corn borer tunneling into stalk and ear shanks, and infection by pathogens such as Colletotrichum graminicola, the causative agent in Anthracnose stalk rot. Adverse fall weather conditions also contribute to late season stalk lodging.
The mechanical strength of the maize stalk plays a major role in a plant's resistance to all types of stalk lodging, and therefore, is of great value to the farmer. Enhancing overall mechanical stalk strength in maize will make stalks stronger during both vegetative development and late season, thereby reducing yield and grain quality losses. Moreover, maize plants with increased mechanical stalk strength can remain in the field for longer periods of time, allowing farmers to delay harvest, if necessary.
Selection through the use of molecular markers associated with mechanical stalk strength has the advantage of permitting at least some selection based solely on the genetic composition of the progeny, and selections can be made very early on in the plant life cycle, even as early as the seed stage. The increased rate of selection that can be obtained through the use of molecular markers associated with mechanical stalk strength means that plant breeding for increased mechanical stalk strength can occur more rapidly.
It is desirable to provide compositions and methods for identifying and selecting maize plants that display overall increased mechanical stalk strength.